Apparatuses and Methods for Power Saving in USB Devices

1. Universal Serial Bus (USB) device having reduced power consumption, the USB device comprising: a bus clock synchronization module configured to measure a bus clock period, wherein the bus clock period is associated with a communication bus connecting the USB device to a host device; and a power control module configured to: i) determine a first power save time period in which an application module of the USB device is to enter a first power save mode, wherein the application module is configured to perform application-specific functionality of the USB device; ii) determine a second power save time period in which the communication bus is to enter a second power save mode, wherein determining the second power save time period is based on the first power save time period and the bus clock period; iii) send a power save request to the host device, wherein the power save request corresponds to a request for the communication bus to enter the second power save mode for the second power save time period; and iv) cause the USB device to enter a third power save mode of operation in response to a reply to the power save request, including causing the application module to enter the first power save mode for the first power save time period by communicating with the application module via an interface separate from the communication bus.

2. The USB device of claim 1 , wherein the power save request includes at least one value corresponding to the second power save time period.

3. The USB device of claim 1 , wherein the third power save mode of operation has a duration based on the second power save time period.

4. The USB device of claim 1 , wherein the request comprises an isochronous transfer including a start time and/or an end time of the second power save time period.

5. The USB device of claim 1 , wherein the first power save time period is based on a traffic indicator beacon interval for a wireless network module.

6. The USB device of claim 5 , wherein the wireless network module is configured to obtain the beacon interval from a wireless access point.

7. The USB device of claim 5 , wherein the power control module is further configured to reduce the power consumption of the wireless network module during the beacon interval by disabling a radio frequency (RF) component and/or a processing component of the wireless network module.

8. The USB device of claim 5 , further comprising the wireless network module.

9. The USB device of claim 1 , wherein the power control module is further configured to reduce the power consumption of a USB physical layer module and/or a USB interface processing module during the third power save mode of operation.

10. The system of claim 9 , wherein the power control module is configured to reduce the power consumption of the USB physical layer module by placing the USB physical layer module in a high speed idle mode.

11. The USB device of claim 9 , wherein the power control module is configured to reduce the power consumption of the USB interface processing module by disabling the USB interface processing module.

12. The USB device of claim 1 , wherein the power control module is further configured to place a USB physical layer module in a high speed idle mode during the third power save mode of operation.

13. The USB device of claim 12 , wherein the host device is configured to: leave the USB device in the high speed idle mode during said third power save mode of operation; and suspend communication with the USB device during the third power save mode of operation.

14. The USB device of claim 1 , wherein the power control module is further configured to enter a bus activity mode of operation after the third power save mode of operation and to re-enter the third power save mode of operation after a wake period.

15. The USB device of claim 14 , wherein the bus clock synchronization module is configured to determine the bus clock period based on start of frame (SOF) packets received from the host during the bus activity mode of operation.

16. The USB device of claim 14 , wherein the wake period is long enough to receive at least two SOF packets.

17. An integrated circuit device comprising the USB device of claim 1 .

18. The integrated circuit device of claim 17 , further comprising a USB physical layer module.

19. A wireless network adapter comprising: the integrated circuit device of claim 17 ; and a wireless network module, wherein the first power save time period is based on a traffic indicator beacon interval for the wireless network module.

20. The wireless network adapter of claim 19 , wherein the wireless network module comprises a personal area network module, a wireless local area network module, and/or a wireless wide area network module.

21. A wireless network node comprising: the wireless network adapter of claim 19 ; and a USB host, wherein the USB host comprises a USB host interface and a host processor adapted to execute a USB interface driver and/or a wireless network driver.

22. A method for reducing power consumption by a Universal Serial Bus (USB) device, wherein the USB device includes a bus clock synchronization module configured to measure a bus clock period and a power control module configured to control the power consumption of the USB device, the method comprising: i) measuring a bus clock period, wherein said bus clock period is associated with a communication bus connecting the USB device to a host device; ii) determining, with the power control module, a first power save time period in which an application module is to enter a first power save mode, wherein the application module is configured to perform application-specific functionality of the USB device; iii) determining, with the power control module, a second power save time period in which the communication bus connecting the USB device to the host device is to enter a second power save mode, wherein determining the second power save time period is based on the first power save time period and the bus clock period; iv) sending a power save request to the host device via the communication bus, wherein the power save request corresponds to a request for the communication bus to enter the second power save mode for the second power save time period; and v) causing, with the power control module, the USB device to enter a third power save mode of operation in response to a reply to the power save request, including causing the application module to enter the first power save mode for the first power save time period by the power control module communicating with the application module via an interface separate from the communication bus.

23. The method of claim 22 , wherein said power the request includes at least one value corresponding to the second power save time period.

24. The method of claim 22 , wherein the third power save mode of operation has a duration based on the second power save time period.

25. The method of claim 22 , wherein the request comprises an isochronous transfer including a start time and/or an end time of the second power save time period.

26. The method of claim 22 , wherein the first power save time period is based on a traffic indicator beacon interval for a wireless network module.

27. The method of claim 26 , further comprising obtaining the beacon interval from a wireless access point.

28. The method of claim 26 , further comprising disabling a radio frequency component of the wireless network module during the third power save mode of operation.

29. The method of claim 22 , further comprising reducing the power consumption of a USB physical layer module during the third power save mode of operation.

30. The method of claim 22 , further comprising causing a USB physical layer module to enter a high speed idle mode during the third power save mode of operation.

31. The method of claim 30 , wherein the host is configured to: leave the USB device in the high speed idle mode during the third power save mode of operation; and suspend communication with the USB device during the third power save mode of operation.

32. The method of claim 22 , further comprising causing the USB device to enter a bus activity mode of operation after the third power save mode of operation and causing the USB device to re-enter the power saving mode of operation after a wake period.

33. The method of claim 32 , wherein measuring the bus clock period comprises measuring a period between start of frame (SOF) packets received from the host during the bus activity mode of operation.

34. The method of claim 33 , wherein the wake period is long enough to receive at least two SOF packets.

35. A computer-readable medium comprising computer-readable instructions adapted to perform the method of claim 22 .